1. Technical Field
The present invention relates to switched communications networks providing voice mail services, more particularly to a system and method for providing communication between voice mailboxes in multiple mailbox systems using Common Channel Signaling (CCS) while obviating or blocking ringing signals.
2. Background Art
Voice mail has become commonplace not only in business usage but also on an individual telephone service subscriber basis through service from a central office. A voice mail system is a specialized computer that stores messages in digital form on a disk. The voice is generally digitized, usually at a much slower rate than the 64 Kb/s signal the central office uses in its switching network. The digitized voice is compressed and stored on a hard disk that maintains the voice mail operating system, system prompts, and greetings, and the messages themselves. A processor controls the compressing, storing, retrieving, forwarding and purging of files. A comprehensive review of exemplary voice mail systems and voice messaging systems is disclosed in U.S. Pat. No. 5,631,948 to Bartholomew et al., the disclosure of which is incorporated in its entirety herein by reference.
The above-incorporated Bartholomew et al. patent discloses a system and method of effecting transfer of a message such as a voice message from one centralized messaging system to another centralized messaging system in a switched communications network having a plurality of central offices connected to subscriber terminals and connected together by trunks. Specifically, the transfer of the message by one centralized messaging system is effected through a common channel signaling network using the existing advanced intelligent network (AIN) implementation of public switched telecommunications networks in the United States.
AIN conventionally provides services based on feature logic and data located at a centralized node in the network, such as a Service Control Point (SCP). Appropriately equipped switches in the network, known as Service Switching Points (SSP's), communicate with the SCP and together they provide various AIN services. The SSP knows which calls require AIN service based on characteristics of the call, such as the line it originated from or the digits that were dialed. The process of identifying calls that require AIN processing is known as "triggering", since a particular characteristic of the call "triggers" to switch into providing AIN treatment. Once a trigger occurs, a query message is sent to the SCP asking for instructions. Based on information contained in the query message, the SCP determines which service is being requested and provides appropriate information such as routing and billing instructions that the SSP then executes to complete the call. Only the SCP "knows" which service is being performed on a particular call. The SSP simply knows how to identify calls that require AIN processing and how to execute instructions provided by the SCP. For this reason, two services that are very different from the viewpoint of the subscriber and the SCP may appear identical to the SSP since it performs the same basic functions for both.
The above-incorporated Bartholomew et al. patent discloses a voice messaging system providing caller to remote mailbox and/or mailbox to remote mailbox communication using TCAP and SS7 messaging in the AIN while blocking or obviating trunking of voice messages. The disclosed system uses existing voice mail equipment interfaced to the telephone network and that is fully responsive to TCAP and SS7 protocols. According to Bartholomew et al., a caller desiring to leave a voice message in the mailbox of a remote person may use a telephone to access his own voice mail system and mailbox and to record the message. The voice processing unit of the mailbox may operate its voice menu to direct the caller to depress a specified key when satisfied with the message. The voice processing unit may then query the caller as to whether he desires to send the message and, if so, to depress another specified key. The voice unit then may instruct the caller as to the procedure for keying in the identity of the destination and to depress a further specified key to send the message. The message is digitized in conventional fashion and stored in the mailbox of the sender. The caller may go on hook after depressing the designated send key. The depression of the send key causes the generation of a tone or other signal which is recognized by the acting SSP as a trigger. This local connection ends usage of the voice network.
The trigger causes the SSP to frame a TCAP inquiry message which is directed to the SCP for instructions. The TCAP message includes information identifying the calling station and mailbox and the called station and the fact that the caller is requesting mailbox to mailbox message transfer. The SCP consults its database to establish whether the caller is authorized to communicate mailbox-to-mailbox and as to the existence and identity of a mailbox for the called number. The SCP then originates a response to the SSP to dispatch one or more SS7 packets to the called directory number and mailbox along with an appropriate routing label and handling instructions and carrying as the included information in the SS7 packet the digitized voice retrieved from the mailbox of the sender. The information may be in T1 protocol which is conventionally the output digital signal of mailbox equipment regardless of manufacture.
Known voice mail systems such as disclosed in Bartholomew et al. are well adapted to efforts to network the voice mail systems. In particular, an organization known as The Message Alliance (TMA) has attempted to establish an open standard for voice mail systems. Work is underway to develop a set of standards known as Audio Message Interchange Service (AMIS) in the hope that when AMIS standards are approved, they will form a common language that network voice mail systems can support to enable communication between voice mail systems of different manufacturers.
In particular, TMA has proposed a voice mail messaging system where a subscriber having voice mail service dials into his or her voice mail system (the originating voice mail system), records a message, and inputs the telephone number of the called party. The originating voice mail system forwards the message and the input telephone number to a protocol translator. The protocol translator is a node connected to the public switched telephone network and that has a first connection for communication with the originating voice mail system and a second connection dedicated to communication with a centralized database. The protocol translator, implemented for example using an IBM RS 6000 system, converts the message and the corresponding telephone number from the protocol used by the originating voice mail system to a protocol compatible with the centralized database (e.g., AMIS). The protocol translator sends the converted message and telephone number to the centralized database via the second dedicated connection using, for example, an Asynchronous Transport Multiplex (ATM) transport layer.
The proposed TMA database stores telephone numbers for all voice mail boxes for all voice mail systems in the TMA network. Hence, all service providers having voice mail subscribers will have the respective voice mail box information stored in the TMA database. Upon receiving a message from the protocol translator, the TMA database will retrieve necessary information for accessing the voice mail box for the called party based on the supplied telephone number, and supply routing information back to the protocol translator. The protocol translator, using the routing information, then initiates a line-sided connection with the public switched telephone network to establish a connection with a destination node serving the voice mail system for the called party.
The disclosed Bartholomew et al. and TMA voice mail systems, however, suffer from the disadvantage that use of an AIN system to perform various call processing transactions results in relatively expensive implementation costs. Specifically, use of AIN components such as the SCP or the ISCP requires purchase, configuration, and maintenance of the AIN components above and beyond the existing switching office network and common channel signaling network. Reliance on the AIN system to perform more functions requires setting more AIN triggers into the switches, resulting in additional delays due to a greater number of TCAP queries that must be processed by either the SCP or the ISCP. Hence, the costs of the AIN system increase substantially as processing capacity of the AIN system needs to be increased by installing a greater number of SCP or ISCP nodes, or by upgrading the processing capacity of existing SCP or ISCP nodes.